BELL’S PALSY A COMPLETE LECTURE NOTES

BELL’S PALSY

Medical Student ➜ Intern ➜ Resident ➜ Consultant | CME-ready | Board-exam high-yield

Learning Objectives: After completing this lecture you should be able to

Define Bell’s palsy and explain its pathophysiology in one sentence.
Distinguish peripheral from central facial palsy at the bedside.
Prescribe evidence-based treatment within the golden 72-hour window.
Predict prognosis and manage ocular & late complications.
Answer common MCQs and viva questions confidently.

📑 Table of Contents (click to expand)

1. Definition & ICD-10
2. Epidemiology & Risk Factors
3. Pathophysiology (Exam-ready)
4. Clinical Features & Bedside Grading
5. Differential Diagnosis – VITAMIN C
6. Investigations – Who Needs What?
7. Evidence-Based Management
8. Ocular Protection Protocol
9. Prognosis & Poor Predictors
10. Complications & Late Reconstruction
11. Special Populations
12. Rapid MCQ Quiz
13. Common Viva Questions
14. Pocket Summary Card

1. Definition & ICD-10

Bell’s palsy = acute, idiopathic, unilateral, peripheral facial-nerve (CN-VII) palsy developing within 72 h and reaching maximum deficit by day-7, after exclusion of secondary causes.

ICD-10: G51.0
Synonyms: Idiopathic facial paralysis, acute peripheral facial palsy

2. Epidemiology & Risk Factors

Numbers
• 15–40 per 100 000 / year
• Lifetime risk ≈ 1 in 60
• Sex: M = F; Age peak 15–45 y
• Recurrence 7–12 % (same side 60 %)

Risk amplifiers
• Pregnancy (3rd trimester & 1st wk post-partum)
• Diabetes mellitus, HTN, obesity
• Recent viral URI, stress, cold exposure

3. Pathophysiology (Exam-ready 60-second answer)

HSV-1 reactivation in geniculate ganglion → CD8+ lymphocytic inflammation → intrafascicular oedema → compression & ischaemia within the narrowest bony segment (labyrinthine canal, 0.7 mm) → segmental demyelination ± axonal degeneration → clinical weakness proportional to pressure & duration.

4. Clinical Features & Bedside Grading

Onset: hours to 2 days; maximal by day-7
Symptoms: unilateral facial weakness (upper + lower face), post-auricular pain 50 %, dry eye, epiphora, hyperacusis, metallic taste, drooling
Signs: loss of nasolabial fold, inability to close eye/blow cheek, positive Bell phenomenon, decreased corneal reflex

House-Brackmann Scale (I–VI) – universally accepted

Grade	Description	Prognosis
I	Normal	—
II	Mild weakness, complete eye closure	Excellent
III	Moderate, obvious but not disfiguring	Good
IV	Disfiguring, incomplete eye closure	Fair
V	Barely perceptible movement	Poor
VI	No movement	Very poor

5. Differential Diagnosis – VITAMIN C

Vascular – Stroke, A-V malformation
Infective – Ramsay Hunt, Lyme, otitis media/cholesteatoma, HIV, sarcoidosis
Trauma – Temporal bone fracture, iatrogenic (parotid surgery)
Aneurysm – Basilar, vertebral, posterior circulation
Mass – CPA tumour, parotid malignancy, facial nerve schwannoma
Inflammatory – Vasculitis, GBS, Melkersson-Rosenthal syndrome
Neoplastic – Leptomeningeal mets, lymphoma
Congenital – Mobius syndrome

6. Investigations – Who Needs What?

Classic presentation <72 h → NONE (AAN 2019)
Red flags → selective:
- Gradual >3 wk, other cranial nerves, nodular parotid → MRI brain/IAC ± parotid US/FNA
- Bilateral, endemic area → Lyme serology, VZV PCR, HIV, ACE, chest CT (sarcoid)
- Trauma, otitis → temporal-bone CT
Electrophysiology: ENoG >90 % degeneration at day-14 → prognostic; consider surgical decompression

7. Evidence-Based Management (Cochrane 2023)

Acute <72 h
Prednisolone 1 mg/kg (max 60 mg) PO daily × 7 d ± taper 5 d → NNT 8 for complete recovery.
Add Valaciclovir 1 g TID × 7 d (small additional benefit, safe).

Pregnancy: category B – same dose; monitor glucose
Diabetes: acceptable; adjust hypoglycaemics
No evidence: acupuncture alone, electrical stimulation monotherapy, hyperbaric oxygen alone

8. Ocular Protection Protocol

Preservative-free artificial tears every 2 h while awake
Carbomer ointment + moisture-chamber (plastic wrap) at night
Warn: red eye, pain, photophobia → same-day slit-lamp
If lagophthalmos >5 mm or loss of Bell phenomenon → temporary tarsorrhaphy or upper-lid gold-weight insertion

9. Prognosis & Poor Predictors (SUNSET)

S – Age >60
U – Complete (HB V–VI)
N – No ear pain (non-inflammatory)
N – SBP >140 mmHg
E – Early loss of taste
T – Time to steroids >3 d

Recovery rates
• HB I–II at 6 m: 70 % untreated → 94 % with steroids
• Persistent deficit: 5–20 %; synkinesis 10 %

10. Complications & Late Reconstructive Options

Exposure keratopathy → opacity, perforation
Synkinesis (eye closure with smile) → BOTOX ± myectomy
Crocodile tears (gustatory lacrimation) → BOTOX to lacrimal gland
Permanent weakness → facial re-animation (gracilis free flap, cross-face nerve graft, temporalis transfer)

11. Special Populations

Pregnancy: same steroid dose; monitor glucose; safe in lactation
Children: prognosis excellent (90 % full recovery); still treat with steroids <72 h (short course)
Diabetes: higher risk of incomplete recovery; tighter glycaemic control during high-dose steroids

12. Rapid MCQ Quiz (Board style)

Q1. A 28-year-old woman presents with 24 h of right facial weakness involving forehead and mouth. Arm drift is normal. Most appropriate next step?

Reveal answer

Start prednisolone 60 mg PO daily – no imaging needed.

Q2. Which feature BEST distinguishes Bell’s from central facial palsy?

Reveal answer

Involvement of forehead muscles (peripheral = weak, central = spared).

13. Common Viva Questions

Q: Pathophysiology in 30 seconds?
A: HSV-1 reactivation → inflammation → canal compartment syndrome → conduction block.
Q: Indications for MRI?
A: Gradual >3 wk, other cranial nerves, bilateral, recurrent same side, parotid mass.
Q: Steroid dose in pregnancy?
A: Same 1 mg/kg – category B, safe.
Q: ENoG threshold for decompression?
A: >90 % degeneration at day-14 + complete clinical palsy.

14. One-Line Pocket Summary

Forehead involved + normal limb = Bell’s → 60 mg prednisolone STAT, lubricate eye, review 1 week